Osmium (VIII) catalyzed kinetics and mechanism of indoles oxidation with Aryl-N-haloamines in alkaline medium

✍ Scribed by K. S. Rangappa; H. Ramachandra; D. S. Mahadevappa; N. M. Made Gowda

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 557 KB
• Volume: 28
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(1996)28:4<265::aid-kin4>3.0.co;2-t

✦ Synopsis

The kinetics of oxidation of the title substrates by sodium N-haloarylsulfonamides (or aryl-Nhaloamines). chlorarnine-T (CAT), bromamine-T (BAT), chlorarnine-B [CAB), and bromamine-B (BABI, catalyzed by osmiurn(Vlll) in alkaline medium has been studied at 30°C The corresponding oxindoles and arylsulfonarnides have been characterized as reaction products The reaction rate shows a first-order dependence each on lindolelo and loxidantllj, a tractional-order on IOs(VIII)I, and an inverse first-order on IOH-1. Addition of arylsulfonamide, chloride and bromide, and variation of ionic strength of the medium have no effect on the reaction rate There is a negative effect of dielectric constant of t h e solvent. Activation parameters have been calculated from the Arrhenius and Eyring plots. Harnrnett correlation of substituent effects indicates an LFE relationship with p = -1 0. showing the formation of an electron deficient transition state From enthalpy-entropy relationships and Exner correlations, the isokinetic temperatures (333 K and 326 K ) have been determined for the reactions of CAT and BAT, respectively Proton inventory studies in H 2 0 -D 2 0 mixtures have shown the involvement of a single exchangeable proton of OH-ion in the transition state A mechanism consistent with the observed kinetics has been proposed 0 1996 lahn Wile) & Sons. Inc